1. Field of the Invention
The invention relates in general to an antenna, and more particularly to an antenna for a plug-and-play device.
2. Description of the Related Art
As wireless communication technology advances, it is a trend that wireless signal transmission will replace wired signal transmission in the near future.
Since the Federal Communications Commission declared the standard of the ultra-wide band (UWB) technology in 2002, researches and inventions relative to the UWB technology have been emerged in great numbers. Although the Federal Communications Commission approved the commercial use of UWB transmissions in the range from 3.1 GHz to 10.6 GHz, now the most widely used band for commercial use is only from 3.1 GHz to 6.0 GHz, which is the lower band of the UWB.
When the band is wider, the data transmission speed is faster. The UWB technology can achieve 100˜500 Mb/s transmission speed, which is much greater than the conventional speed. Also, the UWB technology provides larger transmission capacity. The image transmission can hence be sent wirelessly through the UWB technology easily. The goal to provide the wireless home theater can be achieved accordingly.
Furthermore, the wireless signal transmission between computer peripherals, such as a keyboard, a mouse, a screen, a printer or a fax machine, can be achieved through the UWB technology. In the future, the personal computer only needs to be connected to a universal serial bus (USB) plug-and-play device that has an integrated UWB signal-receiving module for transmitting signals between the computer and the peripherals. Therefore, it is very important to develop a compact UWB antenna for the USB plug-and-play device.
A planar monopole antenna disclosed in Taiwan Patent No. I248,231 and an omni-directional broadband monopole antenna disclosed in Taiwan Patent No. I239,122, the length of the antenna is equal to about 0.18 times the wavelength of the lowest operating frequency. When the trend of the plug-and-play device is toward compact-size devices, the length of the antenna limits the size of the device.